For lithium-ion batteries, the power density is inversely proportional to the lithium-ion transport length. Three-dimensional interpenetrating electrodes have been proposed in which the negative and positive electrode is separated by a thin, conformal electrode coating having submicron and nanoscale dimensions, which controls the transport of charged species such as lithium cations and electrons. In addition to a thin coating separating the electrodes, the negative and positive electrodes are interpenetrating. By directly coating one of the three-dimensional electrodes with the thin coating, however, the two-dimensional planar porous membrane sheets may be replaced. To complete the cell, the second electrode is subsequently applied to the surface of the thin coating.
Quantifying the presence, or absence, of defects or pinholes for such three-dimensional architectures is problematic since the coatings are formed during the fabrication of the energy storage device, unlike for traditional membrane separators that are first manufactured and tested before being incorporated into the electrochemical energy storage device. Such imperfections could result in the unregulated transport of reactive and or charged species through the coating, thereby resulting in unsatisfactory device performance. Further, physical removal of the coating from the electrode surface for subsequent testing would result in irreparable damage to both the coating and the energy storage device.